The present invention relates to an external electrode fluorescent lamp (EEFL) and manufacturing method thereof.
The present invention relates to an external electrode fluorescent lamp (EEFL) and manufacturing method thereof, more particularly, to a manufacturing method of a dual external electrode fluorescent lamp wherein a separate glass tube having a different diameter from that of an electrode-less fluorescent lamp is connected to the both ends of the lamp so that the total length of the external electrode fluorescent lamp and the length of the external electrode could be decreased.
A liquid crystal display is a light-emitting flat display device, but it cannot emit light to form images by itself. Since it is a light-receiving flat display device that has to receive light from outside to form images, it has a problem that the images cannot be seen in darkness.
To solve above problem, a back light is provided on the back face of the liquid crystal display for radiating light so that the images can be seen in darkness. General properties required for the back light may comprise high luminance, high efficiency, uniformity of the luminance, long life, thinness, low weights, and low prices, etc.
In conventional arts, A cold cathode fluorescent lamp (CCFL) had been widely used as the back light, but the problem is that it operates only at high luminance and the effective life of the lamp is short. In this regards, as the back light, the external electrode fluorescent lamp has been widely used recently.
The external electrode fluorescent lamp is a fluorescent lamp having structure to form plasma in the lamp by the electric field of the external electrodes, which is formed at external sides of both ends of the lamp that has gases in a closed glass tube, and which performs the electric discharge operation of the gases without exposure of the electrodes in the discharge space. Although the electric discharge of the gases inside of the tube is the same as that inside a typical lamp, since the glass tube itself acts as a dielectric material and wall charges are added due to the deposition of space charges generated by discharging before the external voltage applied for inducing discharge, a voltage gain generates.
The external electrode fluorescent lamp is one of the next-generation lamps for illumination, having, in contrast to the typical lamp such as the cold cathode fluorescent lamp, etc. its electrodes at outside, using the electron emission by the electric field so that heat cannot be generated, having effect life about five times longer than and brightness about ten times brighter than that of a typical fluorescent lamp, and having energy efficiency about five times greater than that of the cold cathode fluorescent lamp. In addition, as the external electrode fluorescent lamp has more advantages such as the ability of driving multiple tubes with different driving devices, it has been widely used in usages such as LCD TVs, advertisement panels, etc. which require high brightness.
Meanwhile, the diameter of the tube relates to brightness and quantity of light. The smaller the diameter of the tube, the greater the brightness but the smaller the quantity of light as the light emitting area of the fluorescent lamp is smaller. On the other hand, The larger the diameter of the tube, the smaller the brightness but the light emitting area is increased so that the lamp may be applied in a high power lamp that require large quantity of light. Especially, for obtaining high brightness the external electrode fluorescent lamp having thin tube of small diameter has been used, but it's quantity of light is small. For compensating this, if the tube diameter is increased then the brightness will be lowered.
And if the total length of the lamp and the tube diameter are increased then the lengths of the corresponding external electrodes will be lengthened to obtain constant brightness. However, if the lengths of the external electrodes is increased then the effective light emitting area will be decreased, such that when it is used as the back light, the external electrode portion is large and non-light-emitting area of the panel is increased, which acts a negative factor to efficiency of the lamp.
Therefore, according to the usage fields, the lamp having a longer length as well as a larger tube diameter are required for the external electrode fluorescent lamp, but at present above mentioned problems still remain.